Wireless data transmission

ABSTRACT

The subject matter described herein relates to data communication in wireless communication systems. The device determines availability of scheduled serving cell before data communication and informs a device the determined availability of the scheduled serving cell. Depending upon the determined availability, the device is controlled to perform the data communication on the scheduled serving cell or another available serving cell. In this way, the unfinished data communication, for example, retransmission of a data block in an uplink or downlink HARQ process can be continued on an available serving cell, whereby avoiding large transmission delay and throughput loss in the wireless communication system.

RELATED APPLICATIONS

This application is a continuation application that claims priority toU.S. application Ser. No. 14/697,207, filed on Apr. 27, 2015, andentitled “WIRELESS DATA TRANSMSSION”, which claims priority toInternational Application No. PCT/CN2015/000065, filed on Jan. 29, 2015,and entitled “WIRELESS DATA TRANSMISSION.” This application claims thebenefit of the above-identified applications, and the disclosure of theabove-identified applications are hereby incorporated by reference intheir entireties as if set forth herein in full for all intents andpurposes.

TECHNICAL FIELD

The non-limiting and example embodiments of the present disclosuregenerally relate to wireless communications, and specifically to methodsand apparatuses for data transmission in a wireless communicationsystem.

BACKGROUND

In wireless communication, the demand for high data rate keepsincreasing and Long Term Evolution (LTE) developed by the thirdgeneration project partnership (3GPP) has proven an extremely successfulplatform to meet such demand. The LTE system has been designed tooperate in a dedicated and licensed band to avoid interference withother systems and to guarantee satisfying communication performance.However, because the demand for high data rate keeps increasing whileavailable licensed frequency resources keeps shrinking, more and morecellular network operators are considering the utilization of theunlicensed spectrum as a complementary tool to augment their serviceoffering.

One way to utilize an unlicensed band is called “Licensed-AssistedAccess (LAA)”, where the utilization of the unlicensed band is undercontrol from the licensed band. LTE LAA is a topic to be studied in 3GPPLTE-Advanced Rel-13 and beyond. The objective of LTE LAA is toinvestigate the basic aspects for the operator-controlled non-standalonedeployment of LTE in unlicensed spectrum, considering uplink anddownlink or downlink only transmission in the unlicensed spectrum, tofurther improve network throughput and provide offloading capability tomeet the demand of increasing traffic volume.

Particularly, LTE LAA can use carrier aggregation (CA) to aggregate thecarriers in unlicensed spectrum, (e.g., using unlicensed carrier as aSupplemental Downlink or a Component Carrier). In such a scenario, aprimary cell (also called PCell, primary carrier, or primary componentcarrier) for either a LTE frequency division duplex (FDD) or timedivision duplex (TDD) system can always operate in a licensed band tocarry control signaling, mobility management and data, while one or moresecondary cells (also called SCells, secondary carriers, or secondarycomponent carriers herein) in unlicensed band can provide downlink (DL)and/or uplink (UL) data transmission for opportunistic capacityimprovement.

SUMMARY

The unlicensed band is shared by various wireless devices and networks,rather than dedicated for specific use. Therefore, for a systemoperating in the unlicensed band, co-channel interferences from otherwireless systems has to be addressed. To alleviate the interferenceproblem, the listen-before-talk (LBT) feature has been introduced intothe systems operating in the unlicensed band, and has been mademandatory in some countries/regions. This feature has also been agreedupon for LTE LAA in 3GPP RAN1#78bis meeting, and the physical layerdesign of LTE LAA should take the LBT feature into account.Particularly, a LTE Evolved Node B (eNB) or User Equipment (UE) shouldmeasure the unlicensed spectrum before transmitting on the unlicensedspectrum.

The introduction of LBT mechanism may have an impact on datatransmission, especially for Hybrid Automatic Repeat reQuest (HARQ)performance of LAA, because the availability of transmission opportunityon unlicensed band cannot be guaranteed. It results in ongoing datatransmission such as HARQ processes may be interrupted due to therequirement of idle period or unavailability of operating channel aftera Clear Channel Assessment (CCA) check. When the unlicensed channels areheavily loaded, the interruption in data transmission may happenfrequently and retransmission of a data block in the HARQ process may bedelayed for a long time.

In accordance with embodiments of the subject matter described herein,the problem can be alleviated by allowing a device to determineavailability of a scheduled serving cell before data communication andinform other device of the determined availability of the scheduledserving cell. Depending upon the determined availability, the device iscontrolled to perform the data communication on the scheduled servingcell or an available serving cell. In one embodiment of the subjectmatter described herein, the first serving cell may be operated in alicensed band and the second serving cell may be operated in anunlicensed band.

In this way, even if the scheduled serving cell is operated in anunlicensed band and the data transmission is interrupted due to theunavailability of transmission opportunity on the unlicensed band (e.g.,the unfinished uplink or downlink data transmission), retransmission ofa data block in an uplink or downlink HARQ process can be continued onanother available serving cell. As such, large transmission delay andthroughput loss in the wireless communication system can be avoided.

This Summary is provided to introduce a selection of concepts in asimplified form. The concepts are further described below in theDetailed Description. This Summary is not intended to identify keyfeatures or essential features of the claimed subject matters, nor is itintended to be used to limit the scope of the claimed subject matters.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the subject matter described herein are illustrated byway of example and not limited in the accompanying figures in which likereference numerals indicate similar elements and in which:

FIG. 1 illustrates a block diagram of a device in accordance with oneembodiment of the subject matter described herein;

FIG. 2a illustrates a block diagram of an environment in whichembodiments of the subject matter described herein may be implemented;

FIG. 2b illustrates a schematic diagram showing the discontinuedtransmission on the unlicensed band;

FIG. 3 illustrates a flowchart of a method for wireless communication inaccordance with one embodiment of the subject matter described herein;

FIG. 4a illustrates a schematic diagram showing that unfinished datatransmission is continued in the serving cell scheduling the datatransmission;

FIG. 4b illustrates a schematic diagram showing that unfinished datatransmission is continued in another available serving cell;

FIG. 5 illustrates a flowchart of a method for wireless communication inaccordance with another embodiment of the subject matter describedherein;

FIG. 6 illustrates a block diagram of an apparatus for wirelesscommunication in accordance with one embodiment of the subject matterdescribed herein; and

FIG. 7 illustrates a block diagram of an apparatus for wirelesscommunication in accordance with another embodiment of the subjectmatter described herein.

DETAILED DESCRIPTION

The subject matter described herein will now be discussed with referenceto several example embodiments. It should be understood theseembodiments are discussed only for the purpose of enabling those skilledpersons in the art to better understand and thus implement the subjectmatter described herein, rather than suggesting any limitations on thescope of the subject matter.

As used herein, the term “base station” (BS) may represent a node B(NodeB or NB), an evolved NodeB (eNodeB or eNB), a Remote Radio Unit(RRU), a radio header (RH), a remote radio head (RRH), a relay, a lowpower node such as a femto, a pico, and so forth.

As used herein, the term “user equipment” (UE) refers to any device thatis capable of communicating with the BS. By way of example, the UE mayinclude a terminal, a Mobile Terminal (MT), a Subscriber Station (SS), aPortable Subscriber Station (PSS), a Mobile Station (MS), or an AccessTerminal (AT). Specifically, some examples of UEs include devicesoperable in unlicensed band.

As used herein, the term “includes” and its variants are to be read asopen terms that mean “includes, but is not limited to.” The term “basedon” is to be read as “based at least in part on.” The term “oneembodiment” and “an embodiment” are to be read as “at least oneembodiment.” The term “another embodiment” is to be read as “at leastone other embodiment.” Other definitions, explicit and implicit, may beincluded below.

FIG. 1 illustrates a block diagram of a device 100 in accordance withone embodiment of the subject matter described herein. In oneembodiment, the device 100 may be UE, which may be any device withwireless communication capability, such as a mobile phone, a portabledigital assistant (PDA), a pager, a mobile computer, a mobile TV, a gameapparatus, a laptop, a tablet computer, a camera, a video camera, a GPSdevice, and other types of voice and textual communication system. Afixed-type device may likewise easily use embodiments of the subjectmatter described herein.

As shown, the device 100 comprises one or more antennas 112 operable tocommunicate with the transmitter 114 and the receiver 116. With theseantennas, the device 100 may perform cellular communications with one ormore devices, such as BS or other UEs. Specifically, the device 100 maybe configured to operate in a licensed band or an unlicensed band, andmay be configured to perform LBT when operating in an unlicensed band,for example, for contention based access.

The device 100 further comprises at least one controller 120. It shouldbe understood that the controller 120 comprises circuits or logicrequired to implement the functions of the device 100. For example, thecontroller 120 may comprise a digital signal processor, amicroprocessor, an A/D converter, a D/A converter, and/or any othersuitable circuits. The control and signal processing functions of thedevice 100 are allocated in accordance with respective capabilities ofthese devices.

Optionally, the device 100 may further comprise a user interface, which,for example, may comprise a ringer 122, a speaker 124, a microphone 126,a display 128, and an input interface 130, and all of the above devicesare coupled to the controller 120. The device 100 may further comprise acamera module 136 for capturing static and/or dynamic images.

The device 100 may further comprise a battery 134, such as a vibratingbattery set, for supplying power to various circuits required foroperating the device 100 and alternatively providing mechanicalvibration as detectable output. In one embodiment, the device 100 mayfurther comprise a user identification module (UIM) 138. The UIM 138 isusually a memory device with a processor built in. The UIM 138 maycomprise a subscriber identification module (SIM), a universalintegrated circuit card (UICC), a universal user identification module(USIM), or a removable user identification module (R-UIM), etc. The UIM138 may comprise a card connection detecting apparatus according toembodiments of the subject matter described herein.

The device 100 further comprises a memory. For example, the device 100may comprise a volatile memory 140, for example, comprising a volatilerandom access memory (RAM) in a cache area for temporarily storing data.The device 100 may further comprise other non-volatile memory 142 whichmay be embedded and/or movable. The non-volatile memory 142 mayadditionally or alternatively include EEPROM and flash memory. Thememory 140 may store any item in the plurality of information segmentsand data used by the device 100 so as to implement the functions of thedevice 100. For example, the memory may contain machine-executableinstructions which, when executed, cause the controller 120 to implementthe method described below.

It should be understood that the structural block diagram in FIG. 1 isshown only for illustration purpose, without suggesting any limitationson the scope of the subject matter described herein. In some cases, somedevices may be added or removed as required.

FIG. 2a shows an environment of a wireless communication system in whichembodiments of the subject matter described herein may be implemented.As shown in FIG. 2a , one or more UEs may communicate with a BS 200,such as an evolved NodeB (eNodeB). In this example, there are three UEs210, 220 and 230 shown, but this is only for the purpose of illustrationwithout suggesting limitations on the number of UEs. There may be anysuitable number of UEs in communication with the BS 200. In oneembodiment, one or more of the UEs 210, 220 and 230 may be implementedas the device 100 as shown in FIG. 1, for example. In addition, a UE maycommunicate with another UE directly, e.g., via device-to-device (D2D)communication. In the example, D2D paired devices are illustrated by UE220 and UE 230.

The communications between the UEs 210, 220 and 230 and the BS 200, andbetween the UE 211 and the BS 201 may be performed according to anyappropriate communication protocols including, but not limited to, thefirst generation (1G), the second generation (2G), 2.5G 2.75G, the thirdgeneration (3G), the fourth generation (4G) communication protocols,and/or any other protocols either currently known or to be developed inthe future. Though for illustration purpose, in some embodiment of thedisclosure, the UEs 210, 220 and 230 and the BS 200 may communicateusing 3GPP LTE technique, the embodiments of the present disclosure arenot limited to such network scenarios.

The wireless communication system as shown in FIG. 2a may be deployed inboth licensed and unlicensed bands. The unlicensed band may be sharedwith various other wireless systems (for example a Wi-Fi system) in acontention-based way. As shown in FIG. 2a , in a Carrier Aggregation(CA) scenario, the UE 210, for example, is configured with more than oneserving cell (i.e., PCell and SCells). Some serving cells may beoperated in the licensed band, while other serving cells may be operatedin the unlicensed band.

As described above, the introduction of the LBT mechanism may have animpact on data communication, especially for uplink and downlink HybridAutomatic Repeat reQuest (HARQ) performance of LAA. In the downlinktransmission, for example, before a downlink transmission or a burst oftransmissions on an operating carrier of a serving cell, the BS 200 hasto perform a CCA check by energy detection. If the energy level in thecarrier channel exceeds the predefined threshold, the serving cell isconsidered not available, since the corresponding carrier channel isoccupied; otherwise, it may transmit data immediately or in thefollowing frame period. The BS 200 always needs to perform CCA at theend of an idle period after each data transmission. Therefore,discontinuous transmission for LAA is a basic characteristic because theavailability of a transmission opportunity on the unlicensed band cannotbe guaranteed. This results in ongoing data transmission, especially forHARQ processes, which may be interrupted due to the requirement of idleperiod or unavailability of the scheduled serving cell after a CCAcheck. This problem will be described in detail with reference to theexample of FIG. 2 b.

FIG. 2b illustrates a schematic diagram showing the discontinuedtransmission on the unlicensed band in the HARQ process. As shown inFIG. 2b , the first and second serving cells are configured for the UE210 by the BS 200, where the first serving cell may be a PCell or anSCell operating in the licensed band and the second cell may be an SCelloperating in the unlicensed band. The second serving cell (correspondingto SCell, secondary component carrier, or secondary cell) is scheduledby the first serving cell (corresponding to PCell, primary componentcarrier, or primary cell) via Physical Downlink Control CHannel (PDCCH).Initial transmission of data blocks is scheduled to be performed in thesecond serving cell during a time period, for example, a sub-frame (1ms). Before the retransmission for the data blocks that areunsuccessfully received at receiver side, the BS 200 detects theavailability of the second serving cell by performing the CCA check onthe components carrier of the second serving cell. Due to unavailabilityof the unlicensed band in the next time period (for example, theunlicensed band may be occupied by a Wi-Fi system), the retransmissionof data blocks cannot be sent out until the second serving cell isavailable again. Data transmission for the UE 210 may suffer from alarge transmission delay and the system performance may be severelydegraded due to throughput loss.

Embodiments of the subject matter described herein aim to provide asolution to at least partially solve the problems discussed above.

With reference to FIGS. 3-7, various embodiments of the subject matterdescribed herein are set forth in detail.

FIG. 3 illustrates a flowchart of an exemplary method 300 for datatransmission in wireless communication in accordance with one embodimentof the subject matter described herein.

It would be appreciated that the method 300 may be implemented by anetwork node or a device for communicating data blocks with anotherdevice in the wireless communication system, e.g., the BS 200 as shownin FIG. 2. In the embodiment as illustrated in FIG. 3, data transmissionis scheduled by a first serving cell and transmitted by a second servingcell.

As shown in FIG. 3, the method 300 is entered in step S310, where the BS200 determines availability of the second serving cell before datatransmission. In step S320, the BS 200 informs a device, such as the UE210, of the determined availability of the second serving cell. Based onthe determined availability of the second serving cell, in step S330,the BS 200 performs the data communication on one of the second servingcell and a third serving cell. Specifically, if the scheduled secondserving cell is available, the BS 200 performs the data communication inthe second serving cell; otherwise, the BS 200 schedules the datacommunication to be performed in the third serving cell. Since the otherparty of the data communication, such as the UE 210, can be aware of theavailability of the scheduled second serving cell, the other party canknow whether the corresponding data communication should be performed inthe second serving cell or the third serving cell.

According to an embodiment of the subject matter as disclosed herein,the first serving cell may be operated in the licensed band and thesecond cell may be operated in the unlicensed band. The second servingcell, which may be an SCell (also referred to as a secondary componentcarrier or secondary cell), is scheduled by the first serving cell,which may be a PCell (also referred to as a primary component carrier orprimary cell) or a licensed SCell via PDCCH.

In order to set forth the inventive concepts of the subject matter asdisclosed herein, various embodiments will be described with referenceto the scenarios of the downlink HARQ process for LTE LAA. However,those skilled in the art can appreciate that such scenarios of thedownlink HARQ process are only non-limited examples for the purpose ofillustration, but should not be construed as any limitation to claimedscope. For example, some embodiments of the subject matter as disclosedherein may be applicable to uplink data transmission between BS and UE(for example, uplink HARQ processes) or even D2D transmission betweenUEs, with suitable modifications in signaling communication.

FIG. 4a illustrates a schematic diagram 400 showing that an unfinisheddata transmission is continued in the serving cell scheduling the datatransmission.

As shown in FIG. 4a , the data communication, for example, theunfinished HARQ processes on the scheduled second serving cell can becontinued only in the corresponding scheduling first serving cell. Inother words, the third serving cell as described in FIG. 3 may bepre-configured as the first serving cell, which schedules the datacommunication of the second serving cell. When the BS 200 determinesthat the second serving cell is not available for the subsequent datacommunication, the BS 200 may continue the unfinished data communication(for example, the unfinished UL or DL HARQ process) in the first servingcell.

Solution 1

According to one embodiment of the subject matter as disclosed herein,step S320 in FIG. 3 may be implemented by indicating, in downlinkcontrol signaling sent from the first serving cell to the device, thedetermined availability of the second serving cell.

In an exemplary implementation, one bit Channel Availability Indicator(CAI) may be introduced in DL control signaling to indicate whether thesecond serving cell is available or not in the current time period (forexample, the current sub-frame). For example, the DL control signalingmay be DL grant signaling for downlink HARQ processes or UL grantsignaling for uplink HARQ processes.

In the downlink HARQ processes, for example, if the second serving cellis available, the CAI may be set to, for example, 1 and the DL grantincluding the CAI could be used to cross-carrier schedule the PhysicalDownlink Shared CHannel (PDSCH) transmission on the second serving cell.If the second serving cell is not available, the CAI may be set to, forexample, 0 and the DL grant including the CAI could be used to schedulePDSCH on the same carrier with the DL grant (i.e., the first servingcell) in order to perform those subsequent HARQ processes which areunfinished in the second serving cell. The scheduled second serving cellis indicated by a Carrier Indicator Field (CIF) in the DL granttransmitted from the scheduling cell. Advantageously, in some examples,the HARQ process number of those subsequent HARQ processes may be keptunchanged when those HARQ are continued in the first serving cell.

In this implementation, the BS 200 can determine the availability ofeach unlicensed cell by a CCA check and indicate this using the CAI inthe DL grant signaling. If the second serving cell is available, the BS200 may set the CAI to, for example, 1 and transmit PDSCH on the secondserving cell; otherwise, the BS 200 may set the CAI to, for example, 0and transmit PDSCH on the scheduling cell. In this way, the DLretransmission that is unfinished in the second serving cell iscontinued in PDSCH of the first scheduling cell.

The receiving device, such as the UE 210, does not need to do a CCAcheck on each unlicensed cell. After detection of the DL grant on thefirst serving cell, the UE 210 obtains the availability of the secondserving cell by the CAI. If the CAI is set to, for example, 1, the UE210 may try to receive PDSCH transmission on the second serving cell;otherwise, if the CAI is set to, for example, 0, the UE 210 may try toreceive PDSCH transmission on the first serving cell. Since the HARQprocess number is unchanged, when one unfinished HARQ process of thesecond serving cell is continued in the first serving cell, the UE 210can be aware of the corresponding HARQ process of retransmitted PDSCH onthe first serving cell and try to combine the received soft bits withthe same HARQ process number.

Those skilled in the art can appreciate that the operations of the BS200 and the UE 210 in the uplink HARQ processes are similar to those inthe downlink HARQ processes as above described, except for adopting theUL grant to indicate the CAI. Therefore, the detailed descriptionregarding the operations in the uplink HARQ processes is omitted herefor the purpose of conciseness.

Solution 2

According to one embodiment of the subject matter as disclosed herein,step S320 in FIG. 3 may be implemented by indicating the determinedavailability of the second serving cell via physical layer signaling.The physical layer signaling may include a bitmap corresponding at leastto the availability of all serving cells operated on the unlicensedband.

In an exemplary implementation, a Layer 1 (physical layer) signalingcalled Channel Availability Signaling (CAS) may be introduced to carry abitmap corresponding to the availability of all serving cells operatedon the unlicensed band. The bitmap may also correspond to each SCellirrespective of whether an SCell operates on the licensed band or anunlicensed band. The CAS may have same length with a Downlink ControlInformation (DCI) format 1C with a new Radio Network Temporary Identity(RNTI), which is common to all the UEs served by the BS 200 andconfigured/indicated in Radio Resource Control (RRC) signaling. The CASmay be signaled in PCell common search space in one fixed subframe or aspecified subframe configured by RRC signaling within each frame periodor an RRC signaling configured period. In an advantageousimplementation, the time period for which the CAS is updated from the BS200 to UEs (such as the UE 210) may be aligned to the requirements ofLBT. Once the BS 200 obtains the availability of the serving celloperated in the unlicensed band, the BS 200 informs such availabilityinformation in the CAS via physical layer signaling. The UEs (forexample, the UE 210) are aware of the time period of informing the CASand the UEs are capable of detecting CAS content. According to the CAS,the UE 210 can obtain the availability of the second serving cell andthen the UE 210 can determine that the subsequent data transmission willbe continued in one of the first serving cell and the second servingcell based on the availability of the second serving cell.

In this implementation, the BS 200 can determine the availability ofeach unlicensed cell by a CCA check and indicate that by the CASsignaling. In the downlink HARQ processes, for example, if the secondserving cell is available, the corresponding bit value in the CAS mayset to, for example, 1 and the BS 200 will transmit PDSCH on the secondserving cell based on the determined availability; otherwise, thecorresponding bit value in the CAS is set to, for example, 0 and the BS200 will transmit PDSCH on the first serving cell. In this way, the DLretransmission that is unfinished in the second serving cell iscontinued in the PDSCH of the first serving cell. Advantageously, insome examples, the HARQ process number of those subsequent HARQprocesses may be kept unchanged when those HARQ are continued in thefirst serving cell.

The receiving device (for example, the UE 210) does not need to do a CCAcheck on each unlicensed cell. After detection of the CAS signaling inPCell common search space, the UE 210 obtains the availability of eachserving cell. If one serving cell (e.g., the second serving cell) iscross-carrier scheduled by the first serving cell and the bit value inthe CAS signaling corresponding to this serving cell is set to 1, the UE210 may try to receive PDSCH transmission on the second serving cell;otherwise, the UE 210 may try to receive PDSCH transmission on the firstserving cell. Since the HARQ process number is unchanged, when oneunfinished HARQ process of the second cell is continued in the firstserving cell, the UE 210 can determine that the corresponding HARQprocess of retransmitted PDSCH is in the first serving cell and then tryto combine the received soft bits with the same HARQ process number.

Those skilled in the art can appreciate that the operations of the BS200 and the UE 210 in the uplink HARQ processes are similar to those inthe downlink HARQ processes as above described. Therefore, the detaileddescription regarding the operations in the uplink HARQ processes isomitted here for the purpose of conciseness.

FIG. 4b illustrates a schematic diagram 410 showing that unfinished datatransmission is continued in another available serving cell.

As shown in FIG. 4b , the data communication (for example, theunfinished HARQ processes on unlicensed scheduled second serving cell)can be continued in another available serving cell (i.e., the thirdserving cell as described in FIG. 3 may be designated as an availableserving cell). The designated available serving cell may be either thefirst serving cell or another serving cell which is different from thefirst serving cell, or fixed to PCell, although FIG. 4b shows the thirdserving cell as a different one from the first serving cell for thepurpose of simplicity. When the BS 200 determines that the secondserving cell is not available for the subsequent data communication, theBS 200 may continue the unfinished data communication (for example, theunfinished UL or DL HARQ process) in the designated third serving cell.

Solution 3

According to one embodiment of the subject matter as disclosed herein,step S320 in FIG. 3 may be implemented by indicating, in downlinkcontrol signaling sent from the first serving cell to the device, thedetermined availability of the second serving cell. If the secondserving cell is not available, the downlink control signaling includes acarrier index to indicate the designated third serving cell.

In one exemplary implementation, a new field called Available CarrierIndex (ACI) may be introduced in DL controlling signaling. For example,the DL control signaling may be DL grant signaling for downlink HARQprocesses or UL grant signaling for uplink HARQ processes. The ACI fieldmay have the same bit length to the CIF of the DL control signaling. Inthe downlink HARQ processes, for example, If the scheduled secondserving cell indexed by the CIF is available, then the ACI may be set asa default value, such as the same value of the CIF or a zero value. Assuch, this DL grant is used to cross-carrier schedule the PDSCHtransmission on the second serving cell indexed by the CIF. If thescheduled second serving cell indexed by the CIF is not available andanother serving cell is available, then the ACI may be set to designatethe index of this available serving cell, (i.e., the third serving cell)and this DL grant is used to cross-carrier schedule the PDSCHtransmission on the serving cell designated by the ACI in order tocontinue those unfinished HARQ processes of the second serving cellindexed by the CIF. Advantageously, in some examples, the HARQ processnumber of those subsequent HARQ processes may be kept unchanged whenthose HARQ are continued in the first serving cell.

According to this exemplary implementation, in the downlink HARQprocesses, for example, the BS 200 can determine the availability ofeach unlicensed cell by a CCA check. If the scheduled second servingcell indexed by the CIF is available, the BS 200 may set the ACI in theDL grant signaling as the default value, (for example, the same value asthe CIF or a zero value) and transmit PDSCH on the scheduled secondserving cell indexed by the CIF. If the scheduled second serving cellindexed by the CIF is not available and another serving cell isavailable, the BS 200 may use the ACI to indicate the index of thisdesignated available serving cell (i.e., the third serving cell) in theDL grant and transmit PDSCH on this designated available serving cell.

The receiving device (e.g., the UE 210) does not need to do a CCA checkon each unlicensed cell. After detection of the DL grant in the firstserving cell, the UE 210 may firstly check the CIF and ACI. If the ACIis the default value (for example, the same value as the CIF or a zerovalue), the UE may try to receive PDSCH transmission on the scheduledsecond serving cell indexed by the CIF. If the ACI designates thecarrier index of the third serving cell, the UE may try to receive thePDSCH transmission on the third serving cell indexed by the ACI. SinceHARQ process number is unchanged when one unfinished HARQ process ofscheduled cell is continued in the available third serving cell, the UEcan be aware of the corresponding HARQ process of retransmitted PDSCHand try to combine the received soft bits with the same HARQ processnumber.

Those skilled in the art can appreciate that the operations of the BS200 and the UE 210 in the uplink HARQ processes are similar to those inthe downlink HARQ processes as above described, except for adopting theUL grant to indicate the ACI. Therefore, the detailed descriptionregarding the operations in the uplink HARQ processes is omitted herefor the purpose of conciseness.

Solution 4

According to one embodiment of the subject matter as disclosed herein,the method 300 may further comprise a further step (not shown in FIG. 3)in the scheduling procedure from the first serving cell to the secondserving cell, where the BS 200 may indicate, from the first serving cellto the device, a carrier index of the third serving cell via high layersignaling. The step S320 in FIG. 3 may be implemented by indicating thedetermined availability of the second serving cell via physical layersignaling. The physical layer signaling comprises a bitmap correspondingat least to the availability of all serving cells operated on theunlicensed band.

In exemplary implementation, a Layer 1 (physical layer) signaling calledChannel Availability Signaling (CAS) may be introduced to carry a bitmapcorresponding to the availability of all serving cells operated on theunlicensed band. Alternatively, the bitmap may also correspond to eachSCell (irrespective of the corresponding licensed or unlicensed band).The CAS may have same length with Downlink Control Information (DCI)format 1C with Cyclic Redundancy Check (CRC) scrambled by a new RadioNetwork Temporary Identity (RNTI), which is common to all the UEs servedby the BS 200 and configured/indicated in Radio Resource Control (RRC)signaling. The CAS may be signaled in PCell common search space in onefixed sub-frame or a specified sub-frame configured by RRC signalingwithin each frame period or a RRC signaling configured period. In anadvantageous implementation, the time period, for which the CAS isupdated from the BS 200 to UEs (such as the UE 210), may be aligned tothe requirements of LBT.

In this implementation, a new field called Backup Carrier Index (BCI) isintroduced in RRC signaling during the cross-carrier schedulingprocedure from the first serving cell to the second serving cell. Thecarrier index of the backup serving cell may be informed to the device,such as the UE 210, during the cross-carrier scheduling configurationfor the scheduled second serving cell. In some examples, for the sake ofreliability, the BCI may be the carrier index corresponding to alicensed carrier. When the second serving cell is configured by RRCsignaling for cross-carrier scheduling, the BCI field may be added tothe corresponding RRC signaling to indicate the index of its backupcarrier. The BCI may be reserved, even if a serving cell on licensedband is configured for cross-carrier scheduling. In some examples, thePCell may be always designated as the backup serving cell. In this way,the BCI field in the RRC signaling for cross-carrier scheduling may bereserved or not needed.

According to this implementation, the BS 200 can determine theavailability of each unlicensed cell by a CCA check and indicate that bythe CAS in physical layer signaling. In the downlink HARQ processes, forexample, if the second serving cell is available, the corresponding bitvalue in the CAS may be set to, for example, 1 and the BS 200 maytransmit PDSCH on this scheduled second serving cell; otherwise, thecorresponding bit value in the CAS may be set to, for example, 0 and theBS 200 may transmit PDSCH on the backup carrier indexed by the BCI tocomplete the unfinished HARQ processes.

The receiving device (for example, the UE 210) does not need to do a CCAcheck on each unlicensed cell. After detection of the CAS signaling inPCell common search space, the UE 210 can know the availability of eachserving cell. When one SCell (e.g., the second serving cell) iscross-carrier scheduled by another serving cell (e.g., the first servingcell and the bit value in the CAS signaling corresponding to the secondserving cell is set to, for example, 1), the UE 210 may try to receivePDSCH transmission on this scheduled second serving cell; otherwise, theUE 210 may try to receive PDSCH transmission on its corresponding backupcarrier indexed by the BCI. Since the HARQ process number is unchanged,the UE 210 can determine that the corresponding HARQ process ofretransmitted PDSCH on the backup carrier and try to combine thereceived soft bits with the same HARQ process number.

Those skilled in the art can appreciate that the operations of the BS200 and the UE 210 in the uplink HARQ processes are similar to those inthe downlink HARQ processes and the detailed description thereof isomitted here for the purpose of conciseness.

FIG. 5 illustrates a flowchart of a method 500 for wirelesscommunication in accordance with another embodiment of the subjectmatter described herein.

It would be appreciated that the method 500 may be implemented by a UEor a device for communicating data blocks with another device in thewireless communication system, e.g., the UE 210 as shown in FIG. 2. Inthe embodiment as illustrated in FIG. 5, data communication is scheduledfrom a first serving cell.

As shown in FIG. 5, the method 500 is entered in step S510, where the UE210 obtains availability of the second serving cell. In step S520, theUE 210 performs data communication on one of the second serving cell anda third serving cell, based on the obtained availability of the secondserving cell. According to one embodiment of the subject matter asdisclosed herein, the first serving cell may be operated in a licensedband and the second serving cell may be operated in an unlicensed band.

According to one embodiment of the subject matter as disclosed herein,the third serving cell may be the first serving cell. In one exemplaryimplementation, the UE 210 may obtain the availability of the secondserving cell by receiving, from the first serving cell, downlink controlsignaling including an indicator of the availability of the secondserving cell. In another exemplary implementation, the UE 210 may obtainthe availability of the second serving cell by receiving physical layersignaling including a bitmap corresponding at least to the availabilityof all serving cells operated on the unlicensed band.

According to one embodiment of the subject matter as disclosed herein,the third serving cell is a designated available serving cell. In oneexemplary implementation, the UE 210 may obtain the availability of thesecond serving cell by receiving, from the first serving cell, downlinkcontrol signaling indicating the availability of the second servingcell. The downlink control signaling may include a carrier index of thethird serving cell in case the second serving cell is not available. Inanother exemplary implementation, the UE 210 may receive high layersignaling including a carrier index of the third serving cell and the UE210 may obtain the availability of the second serving cell by receivingphysical layer signaling including a bitmap corresponding at least tothe availability of all serving cells operated on the unlicensed band.

FIG. 6 illustrates a block diagram of an apparatus 600 for wirelesscommunication in accordance with one embodiment of the subject matterdescribed herein. The apparatus 600 can be implemented as, the BS 200shown in FIG. 2, or at least a part thereto. Alternatively oradditionally, the apparatus 600 may be implemented as any other suitableentity in the wireless communication system. The apparatus 600 isoperable to carry out the example method 300 described with reference toFIG. 3 and possibly any other processes or methods. It is also to beunderstood that the method 300 described with reference to FIG. 3 is notnecessarily carried out only by the apparatus 600. At least some stepsof the method 300 can be performed by one or more other entities, suchas specific functional entities in the wireless communication system.

As shown in FIG. 6, the apparatus 600 comprises a determining unit 610,a first transmitting unit 620 and a data transceiving unit 630. Thetransmitting unit 610 and the data transceiving unit 620 are functionalmodules for performing the functionalities of the apparatus 600 inrelation to the embodiments of the present subject matter as disclosedherein, rather than specific physical transmitter or transceiver. Thefirst transmitting unit 620 and the data transceiving unit 630 may beimplemented by radio transceiver, antenna array and relevant processingand memory circuitry so as to perform control signaling and datatransmission.

The determining unit 610 is configured to determine availability of thesecond serving cell, which is scheduled from the first serving cell forperforming data communication, for example, during a HARQ process. Thescheduling first serving cell may be operated in a licensed band and thescheduled second serving cell may be operated in an unlicensed band. Thefirst transmitting unit 620 is configured to inform UE of the determinedavailability of the second serving cell. And the data transceiving unit630 is configured to perform the data communication on one of the secondserving cell and a third serving cell, based on the availability of thesecond serving cell determined by the determining unit 610.

According to one embodiment of the present subject matter as disclosedherein, the third serving cell may be the first serving cell thatschedules the second serving cell. In an exemplary implementation, thefirst transmitting unit 620 may be configured to transmit to the UE, viathe first serving cell, downlink control signaling including anindicator to indicate the availability of the second serving cell. Inanother exemplary implementation, the first transmitting unit 620 may beconfigured to transmit to the UE physical layer signaling including abitmap corresponding at least to the availability of all serving cellsoperated on the unlicensed band.

According to one embodiment of the present subject matter as disclosedherein, the third serving cell is a designated available serving cell.In an exemplary implementation, the first transmitting unit 620 isconfigured to transmit to the UE, via the first serving cell, downlinkcontrol signaling including an available carrier index, designating theavailable serving cell to perform the subsequent data transmission. Incase the second serving cell is not available, the available carrierindex indicates a carrier index of the third serving cell. In anotherexemplary implementation, the apparatus 600 may comprise a secondtransmitting unit (not shown in FIG. 6) configured to transmit to theUE, via the first serving cell, high layer signaling including a carrierindex of the third serving cell. In this implementation, the firsttransmitting unit 620 may be configured to transmit physical layersignaling including a bitmap corresponding at least to the availabilityof all serving cells operated on the unlicensed band.

As described above, the apparatus 600 may be used to improve measurementin both a licensed and unlicensed bands.

FIG. 7 illustrates a block diagram of an apparatus 700 for wirelesscommunication in accordance with another embodiment of the subjectmatter described herein. The apparatus 700 can be implemented as, the UE210 shown in FIG. 2, or at least a part thereto. Alternatively oradditionally, the apparatus 700 may be implemented as any other suitableentity in the wireless communication system. The apparatus 700 isoperable to carry out the example method 500 described with reference toFIG. 5 and possibly any other processes or methods. It is also to beunderstood that the method 500 described with reference to FIG. 5 is notnecessarily carried out only by the apparatus 700. At least some stepsof the method 500 can be performed by one or more other entities, suchas specific functional entities in the wireless communication system.

As shown in FIG. 7, the apparatus 700 comprises an obtaining unit 710and a data transceiving unit 720.

The obtaining unit 710 is configured to obtain availability of thesecond serving cell. The data transceiving unit 720 is configured toperform data communication on one of the second serving cell and a thirdserving cell, based on the availability of the second serving cellobtained by the obtaining unit 710. According to one embodiment of thesubject matter as disclosed herein, the first serving cell may beoperated in a licensed band and the second serving cell may be operatedin an unlicensed band.

According to one embodiment of the subject matter as disclosed herein,the third serving cell may be the first serving cell. In one exemplaryimplementation, the obtaining unit 710 may be configured to obtain theavailability of the second serving cell by receiving, from the firstserving cell, downlink control signaling including an indicator toindicate the availability of the second serving cell. In anotherexemplary implementation, the obtaining unit 710 may be configured toobtain the availability of the second serving cell by receiving physicallayer signaling including a bitmap corresponding at least to theavailability of all serving cells operated on the unlicensed band.

According to one embodiment of the subject matter as disclosed herein,the third serving cell is a designated available serving cell. In oneexemplary implementation, the obtaining unit 710 may be configured toobtain the availability of the second serving cell by receiving, fromthe first serving cell, downlink control signaling indicating theavailability of the second serving cell. The downlink control signalingmay include a carrier index of the third serving cell in the case thatthe second serving cell is not available. In another exemplaryimplementation, the UE 210 may comprises a receiving unit (not shown inFIG. 7) configured to receive high layer signaling including a carrierindex of the third serving cell. In this implementation, the obtainingunit 710 may be configured to obtain the availability of the secondserving cell by receiving physical layer signaling including a bitmapcorresponding at least to the availability of all serving cells operatedon the unlicensed band.

It is to be understood that, though in some embodiments of the subjectmatter described herein, methods and apparatus are described in thecontext of a cellular system, particularly a LTE LAA system, embodimentsof the subject matter described herein are not limited thereto.

The modules/units included in the apparatuses 600 and/or 700 may beimplemented in various manners, including software, hardware, firmware,or any combination thereof. In one embodiment, one or more units may beimplemented using software and/or firmware, for example,machine-executable instructions stored on the storage medium. Inaddition to or instead of machine-executable instructions, parts or allof the units in the apparatuses 600 and/or 700 may be implemented, atleast in part, by one or more hardware logic components. For example,and without limitation, illustrative types of hardware logic componentsthat can be used include Field-programmable Gate Arrays (FPGAs),Application-specific Integrated Circuits (ASICs), Application-specificStandard Products (ASSPs), System-on-a-chip systems (SOCs), ComplexProgrammable Logic Devices (CPLDs), and the like.

In addition, some units or modules in the apparatus 600 or 700 can becombined in some implementations. For example, in one embodiment, it ispossible to use a single transceiver to function as the transmittingunit 620 and the data transceiving unit 630 in the apparatus 600 asdiscussed above. Likewise, a single transceiver may function as theobtaining unit 710 and the data transceiving unit 720 in the apparatus700 as discussed above.

Generally, various embodiments of the subject matter described hereinmay be implemented in hardware or special purpose circuits, software,logic or any combination thereof. Some aspects may be implemented inhardware, while other aspects may be implemented in firmware or softwarewhich may be executed by a controller, microprocessor or other computingdevice. While various aspects of embodiments of the subject matterdescribed herein are illustrated and described as block diagrams,flowcharts, or using some other pictorial representation, it will beappreciated that the blocks, apparatus, systems, techniques or methodsdescribed herein may be implemented in, as non-limiting examples,hardware, software, firmware, special purpose circuits or logic, generalpurpose hardware or controller or other computing devices, or somecombination thereof.

By way of example, embodiments of the subject matter can be described inthe general context of machine-executable instructions, such as thoseincluded in program modules, being executed in a device on a target realor virtual processor. Generally, program modules include routines,programs, libraries, objects, classes, components, data structures, orthe like that perform particular tasks or implement particular abstractdata types. The functionality of the program modules may be combined orsplit between program modules as desired in various embodiments.Machine-executable instructions for program modules may be executedwithin a local or distributed device. In a distributed device, programmodules may be located in both local and remote storage media.

Program code for carrying out methods of the subject matter describedherein may be written in any combination of one or more programminglanguages. These program codes may be provided to a processor orcontroller of a general purpose computer, special purpose computer, orother programmable data processing apparatus, such that the programcodes, when executed by the processor or controller, cause thefunctions/operations specified in the flowcharts and/or block diagramsto be implemented. The program code may execute entirely on a machine,partly on the machine, as a stand-alone software package, partly on themachine and partly on a remote machine or entirely on the remote machineor server.

In the context of this disclosure, a machine readable medium may be anytangible medium that may contain, or store a program for use by or inconnection with an instruction execution system, apparatus, or device.The machine readable medium may be a machine readable signal medium or amachine readable storage medium. A machine readable medium may includebut not limited to an electronic, magnetic, optical, electromagnetic,infrared, or semiconductor system, apparatus, or device, or any suitablecombination of the foregoing. More specific examples of the machinereadable storage medium would include an electrical connection havingone or more wires, a portable computer diskette, a hard disk, a randomaccess memory (RAM), a read-only memory (ROM), an erasable programmableread-only memory (EPROM or Flash memory), an optical fiber, a portablecompact disc read-only memory (CD-ROM), an optical storage device, amagnetic storage device, or any suitable combination of the foregoing.

Further, while operations are depicted in a particular order, thisshould not be understood as requiring that such operations be performedin the particular order shown or in sequential order, or that allillustrated operations be performed, to achieve desirable results. Incertain circumstances, multitasking and parallel processing may beadvantageous. Likewise, while several specific implementation detailsare contained in the above discussions, these should not be construed aslimitations on the scope of the subject matter described herein, butrather as descriptions of features that may be specific to particularembodiments. Certain features that are described in the context ofseparate embodiments may also be implemented in combination in a singleembodiment. Conversely, various features that are described in thecontext of a single embodiment may also be implemented in multipleembodiments separately or in any suitable sub-combination.

Although the subject matter has been described in language specific tostructural features and/or methodological acts, it is to be understoodthat the subject matter defined in the appended claims is notnecessarily limited to the specific features or acts described above.Rather, the specific features and acts described above are disclosed asexample forms of implementing the claims.

We claim:
 1. A method for wireless communication, comprising:determining availability of a second serving cell before datacommunication, wherein the data communication is scheduled from a firstserving cell; informing a device of the determined availability of thesecond serving cell through downlink control signaling; and performingthe data communication on one of the second serving cell or a thirdserving cell after the availability is determined of the second servingcell, wherein the third serving cell the third serving cell isconfigured as the first serving cell, and the third serving cellschedules the data communication of the second serving cell.
 2. Themethod of claim 1, wherein the first serving cell is operated in alicensed band and the second serving cell is operated in an unlicensedband.
 3. The method of claim 1, further comprising directing the firstserving cell to schedule the second serving cell, via a PhysicalDownlink Control Channel (PDCCH), to perform the data communication. 4.The method of claim 1, further comprising: determining the secondserving cell is available; and incident to the second serving cell beingavailable, performing the data communication on the second serving cellinstead of the third serving cell.
 5. The method of claim 1, furthercomprising: determining the second serving cell is unavailable; andincident to the second serving cell being unavailable, performing thedata communication on the third serving cell.
 6. The method of claim 1,wherein informing the device of the determined availability of thesecond serving cell comprises: indicating the determined availability ofthe second serving cell via physical layer signaling, wherein thephysical layer signaling comprises a bitmap corresponding at least tothe availability of a plurality of serving cells operated on theunlicensed band.
 7. The method of claim 1, wherein said informing thedevice of the determined availability of the second serving cellcomprises indicating, in downlink control signaling sent from the firstserving cell to the device, the determined availability of the secondserving cell.
 8. The method of claim 7, wherein the downlink controlsignaling includes a carrier index of the third serving cell because thesecond serving cell is not available.
 9. The method of claim 1, whereinthe data communication is communicated using an uplink or a downlinkHybrid Automatic Repeat reQuest (HARQ) process.
 10. The method of claim1, wherein availability of the second serving cell is indicated in aone-bit Channel Availability Indicator (CAI).
 11. A method forperforming data transmission of a wireless communication from a userdevice using one or more of a first serving cell, a second serving cell,or a third servicing cell, comprising: determining availability of asecond serving cell before the data communication, wherein availabilityof the second serving cell is indicated in a one-bit ChannelAvailability Indicator (CAI); obtaining availability of a second servingcell; and performing data communication on one of the second servingcell or a third serving cell based on the obtained availability of thesecond serving cell, wherein the data communication is partiallytransmitted using the second serving cell and partially transmittedusing the third serving cell.
 12. The method of claim 11, wherein thedownlink control signaling comprises downlink grant signaling for one ormore downlink or uplink Hybrid Automatic Repeat reQuest (HARQ)processes.
 13. The method of claim 11, further comprising: determiningthe second serving cell is available; and incident to saiddetermination, cross-carrier scheduling a Physical Downlink SharedChannel (PDSCH) on the second serving cell.
 14. The method of claim 11,further comprising: determining the second serving cell is unavailable;and incident to said determination, scheduling a Physical DownlinkShared Channel (PDSCH) on the third serving cell.
 15. An apparatus forwireless communication, comprising: a determining unit configured todetermine availability of a second serving cell operated in anunlicensed band before data communication, wherein the datacommunication is scheduled by a first serving cell operated in alicensed band; a first transmitting unit configured to inform UserEquipment (UE) of the determined availability of the second serving cellthrough downlink control signaling; and a data transceiving unitconfigured to perform the data communication on one of the secondserving cell or a third serving cell, based on the determinedavailability of the second serving cell, wherein the third serving cellis a designated available serving cell, wherein the first transmittingunit is configured to transmit, via the first serving cell, the downlinkcontrol signaling including an available carrier index, and wherein inthe case that the second serving cell is not available, the availablecarrier index indicates a carrier index of the third serving cell. 16.The apparatus of claim 15, wherein availability of the second servingcell is indicated in a one-bit Channel Availability Indicator (CAI). 17.The apparatus of claim 15, wherein the data communication is partiallytransmitted using the second serving cell and partially transmittedusing the third serving cell.
 18. The apparatus of claim 15, wherein thedownlink control signaling comprises downlink grant signaling for one ormore downlink or uplink Hybrid Automatic Repeat reQuest (HARQ)processes.
 19. The apparatus of claim 15, wherein the third serving cellis configured as the first serving cell, and the third serving cellschedules the data communication of the second serving cell.
 20. Theapparatus of claim 15, wherein the third serving cell is a designatedavailable serving cell, wherein a second transmitting unit is configuredto transmit, via the first serving cell, high layer signaling includinga carrier index of the third serving cell, and wherein the firsttransmitting unit is configured to transmit physical layer signalingincluding a bitmap corresponding at least to the availability of allserving cells operated on the unlicensed band.